How phase 1/2/3 trial was conducted among children The Phase 1/2/3 trial initially enrolled up to 4,500 children ages 6 months to <12 years of age in the United States, Finland, Poland, and Spain from more than 90 clinical trial sites.
It was designed to evaluate the safety, tolerability, and immunogenicity of the Pfizer-BioNTech vaccine on a two-dose schedule (approximately 21 days apart) in three age groups: ages 5 to <12 years; ages 2 to <5 years; and ages 6 months to <2 years.
Based on the Phase 1 dose-escalation portion of the trial, children 5 to <12 years of age received a two-dose schedule of 10 μg each while children under age 5 received a lower 3 μg dose for each injection in the Phase 2/3 study.